---
name: "gnutls_certificate_client_set_retrieve_function"
section: "3"
platform: "linux"
package: "gnutls-doc"
version: "3.3.8-6+deb8u7"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_certificate_client_set_retrieve_function"
---

# gnutls\_certificate\_client\_set\_retrieve\_function(3)

API function

## NAME

gnutls\_certificate\_client\_set\_retrieve\_function - API function

## SYNOPSIS

**#include \<gnutls/compat.h\>**

**void gnutls\_certificate\_client\_set\_retrieve\_function(gnutls\_certificate\_credentials\_t** *cred***, gnutls\_certificate\_client\_retrieve\_function \*** *func***);**

## ARGUMENTS

- gnutls\_certificate\_credentials\_t cred

  is a **gnutls\_certificate\_credentials\_t** structure.

- gnutls\_certificate\_client\_retrieve\_function \* func

  is the callback function

## DESCRIPTION

This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. You are advised to use **gnutls\_certificate\_set\_retrieve\_function2()** because it is much more efficient in the processing it requires from gnutls.

The callback's function prototype is: int (\*callback)(gnutls\_session\_t, const gnutls\_datum\_t\* req\_ca\_dn, int nreqs, const gnutls\_pk\_algorithm\_t\* pk\_algos, int pk\_algos\_length, gnutls\_retr\_st\* st);

 *req\_ca\_cert* is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. Normally we should send a certificate that is signed by one of these CAs. These names are DER encoded. To get a more meaningful value use the function **gnutls\_x509\_rdn\_get()**.

 *pk\_algos* contains a list with server's acceptable signature algorithms. The certificate returned should support the server's given algorithms.

 *st* should contain the certificates and private keys.

If the callback function is provided then gnutls will call it, in the handshake, if a certificate is requested by the server (and after the  certificate request message has been received).

The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated.

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: http://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2014 Free Software Foundation, Inc..\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- http://www.gnutls.org/manual/